sciencehabit writes "Lying in bed, unable to move a muscle, so-called locked-in patients have few ways to communicate with the outside world. But researchers have now found a way to use the widening and narrowing of the pupils to send a message, potentially helping these patients break the silence. The trick is a webcam-like setup that tracks pupil dilation. When people focus on a hard problem--say a math problem--their pupils dilate. Employing the approach, some locked-in patients could answer 'yes' and 'no' questions just by dilating their eyes."